Process and device for carrying out chemical reactions at high temperatures



June 14, 1960 w. KRAUSE ETAL 2,941,021

PROCESS AND DEVICE FOR CARRYING OUT CHEMICAL REACTIONS AT HIGHTEMPERATURES Filed May 8, 1956 i Figl2 5' 1 7 \Eh Fig.3

Walter Krouse Werner Fischer Rudolf Wirrz Hormur Schilken INVENTORS BYchnfi 4yonah r sa%ad ilnited States iatent G raocnss AND DEVICE nonCARRYING our gHEMICAL REACTIONS AT HIGH TEMPERA- Walter Krause,Frankfurt am Main, Werner Fischer, Bad Soden am Taunus, and Rudolf Wirtzand Hartmut Schilken, Frankfurt am Main, Germany, assignors to FarbwerkeHoechst Aktiengesellschaft vormals Meister Lucius & Briining, Frankfurtam Main, Germany, a corporation of Germany Filed May 8, 1956, Ser. No.583,567

Claims priority, application Germany May 13, 1955 11 Claims. (Cl.260-679) The present invention relates to a process and to a device forcarrying out chemical reactions at high temperatures.

It is known that the production of acetylene, ethylene and higherolefins from methane, ethane or higher bydrocarbons requires supplyingWithin the shortest possible time the hydrocarbons to be reacted withgreat amounts of energy.

Thus, for example, the energy may be supplied indirectly by passing thegases to be cracked through outsideheated pipes or heat exchangers. Thismethod involves the disadvantage that the Walls of the pipes aresuperheated and thus give rise to pronounced formation of coke and soot.Furthermore, the process referred to above is restricted to the use ofsmall diameter pipes, since a pipe of greater size in diameter enablesonly too slow and incomplete a heat transfer from the walls to the gas.The gases in the border zones become too hot contrary to the gases inthe middle zones which become insufiiciently hot and, therefore, do notparticipate in the reaction.

For the indirect supply of heat there are also used so calledregenerative furnaces heated with a gas mixture obtained by combustionof fuel with air; heating is then interrupted, the furnace is cleansedwith an inert gas and then charged with the hydrocarbons to be crackedat the hot filling material of the furnaces. The furnace is again heatedwith heating gas after a minimum temperature has been reached. Thisoperation is continually repeated by automatic commutation in intervalsof some minutes. Detrimental to this process is, in addition to thecomplicated reversing automatic, the inevitable deposition of tarrysubstances in the regenerative furnace and the constantly changingtemperature of the furnace which jeopardize economy and the yieldsobtained.

According to another process the energy required for cracking issupplied direct by subjecting part of the hydrocarbon to be cracked to acombustion process in a special combustion device with oxygen, wherebythe hydrocarbon itself furnishes the energy for pyrolizing thehydrocarbon in excess. This process is however not applicable when it isdesired to prevent the hydrocarbon to be cracked from partialcombustion.

Therefore, it has repeatedly been proposed to supply the energy by meansof a carrier gas, for example hydrogen or combustion gases such as steamheated to a high temperature, which is then mixed in suitable mannerwith the hydrocarbons to be cracked. In this case, it is especiallyadvantageous to use as fuel hydrogen and to subject this substancetogether with oxygen to a combustion process since, after the reaction,the steam formed can be easily separated from the resulting gas bycondensation and since the subsequent separation of the gas is therebyrendered less ditficult. As combustion gas there may also be used allproducts obtained by combustion of any combustible substance.Furthermore, it is particularly advantageous to perform the combustionof the fuel within a fairly small space and to provide for as short adistance as possible between the end of the combustion zone and theinlet for the hydrocarbon to be cracked, so that the inevitable heatlosses caused by dissipation are kept as small as possible. As resultstherefrom, a fairly short flame shall be produced which furnishes greatamounts of energy but burns only on a short distance.

To this end, the fuel and the oxidizing agent are often premixed in aseparate mixing chamber before they are introduced into the combustionchamber proper for combustion. The combustion devices which aresuppliedwith pre-mixed gases involve however the risk that the flame flashesback into the mixing chamber and destroys the. combustion device unlessthe gas supply lines are provided with very sensitive and in most casestechnically complicated control devices which maintain constant pressureand velocity of flow of the mixture of oxygen and vaporized or gaseousfuel, such as hydrogen, as is the case with combustion devices used forthe incomplete combustion of methane or earth gas with oxygen.

All these disadvantages are overcome by our present invention whichcomprises a combustion chamber for performing any pyrolytic reaction;more particularly, our present invention relates to the production ofacetylene and/ or ethylene and/ or higher olefinic hydrocarbons, whereinfuel and oxidizing agent are completely mixed only after the componentshave reached the flame so that just as short a flame is produced as inthe case where the flame is produced by the supply of pre-mixed gases.According to the process of this invention finely divided liquid,vaporized or gaseous fuel and at least one oxidizing gas are introducedseparately into the combustion chamber at a velocity corresponding to aMach-number of at least 0.8, preferably at sonic speed, via at least onetangential bore hole arranged in at least one plane in or opposite tothe direction of rotation and then subjected to a combustion process. Inthis case one of the reactants may be introduced wholly or partially viaradial bore holes. =By mixing and whirling in the manner describedabove, fuel and oxidizing agent undergo so rapid a combustion that theresulting flame ceases to burn after a very short distance. It is,therefore, possible to operate the combustion chamber with very highcharges. Industrially, it is especially advantageous to operate thecombustion chamber with charges of 1 billion or more Kcal/mFh (10 Kcal)The combustion chamber as used in the process of this invention involvesthe particular advantage that the whole combustion process is performedWithin the smallest space-as is the case of flames produced withpremixed gasesso that the heat losses caused by dissipation are small inrelation to the energy produced; contrary to the known devices, acombustion chamber as used herein prevents the flame from flashing backinto the mixing chamber and requires no complicated control mechanism.

The term Mach-number used herein is to define the gas velocity appliedin relation to the sonic speed at the corresponding temperature.

The operating procedure according to'this invention involves the furtheradvantgae that the combustion gases leaving the combustion chamber atflame temperature possess such a high turbulence-due to their havingbeen whirled in said chamberthat they are practically instantaneouslymixed with the reactant to be pyrolized. Thus, the heat is especiallyWell transferred from the combustion gas to the reactants, whereby it ispossible to perform a practically complete reaction.

The reactant to be pyrolized can be introduced into the combustionchamber radially or tangentially either of the oxidizing agent andreversely. The fuel and the oxidizing agent may, howevenalso be'introduced through proper-:bore rings."

' When his desired to prepare acetylene 'and/ or ethylene and/or higherolefin-containing' gases, iLe. gases which in addition to acetyleneand/or ethylene contain propylene, n-butylene, iso-butylene, etc. thatis chiefly o lefins with 3 or 4 carbon atoms, it is especially suitablet adv mix between the flame end and the place where the reactantisintroduced asecondary gas, preferably steam and/or hydrogen in orderto reduce the proportion of oxygen-containing radicals, oxygen atoms andoxygen molecules as it is described in copending patent applicationSerial No. 578,581, filed'April 17, 1956 for Mann-.

facture of Low Molecular Unsaturated Hydrocarbons. This operatingprocedure is especially suitable if fuels are used that produce flamesand combustion gases, such' as have very high temperatures, for examplehydrogen. In this case, the secondary gas can be introduced into thecombustion gas radially or tangentially and both" in and opposite to thedirection of rotation.

For the production of acetylene and/ or ethylene and/or other olefinscontaining 2 to 4 carbon atoms using a combustion device according tothis invention-,jaliphatic' hydrocarbons which may have been pre-heatedareintroduced in gaseous or liquid. form-which term here 4 r ethyleneand/0r higher hydrocarbons there may be used any gaseous or otherhydrocarbons as. far as they are liquid or can be liquefied by heating.Such fuels are used in a finely divided form for operating thecombustion chamber according to this invention and for the production ofthe aforesaid unsaturated hydrocarbons. The term finely dividedjform asused herein shall comprise fine atoririzationofliq'uid hydrocarbons andshall 'alsocomprise th e use of gaseous and vaporous hydrocarbons. Asfuels there may also be'used hydrogen, carbon monoxide or water gaswhich contains an excess of hydrogen and/0r carbon monoxide. 'Insomecases it is advisable V to use commerciallhydrogeu.

. As' oxidizing :agent there mayadyarita'geohsly be used commercial,pure oxygen, if desired .in' admixture with air, the oxidizing agent bing always employed in a theoretically insufficient-quantity. i

A combustion device suitable for use in carryinggout the process of thisinvention is shown diagrammatically in the accompanying drawing,wherein:

Figure 1 is a schematic view in elevation; and

Figures Zand 3 are sections taken through section line AA and BB,respectively, of Figure 1.

In the drawing the numerals designate the following parts:

. Metal chamber 1 surrounded by a coolinguagent, for example water, issupplied through tangential borehole 2 with hydrogen and throughtangential bore hole 3 with oxygen. As shown in Figure 2, hydrogen andoxygen are supplied alternately in one or several superimposed planes.Steam is introduced through holes 4- radially or tangentially'by way ofinlet 4 at the end of the flame.

, The hydrocarbons to be cracked are also introduced radiand below shallinclude the vapo-urized' state-either radi ally or tangentially or inany other knownmanner into thecurrent of combustion gases in order to bemixed action chamber, "for example the reaction tube, with ceramicmaterial to suppress undesirable soot formation which is favored bymetal surfaces.

For designing the combustion chamber it is expedient I to use a metalwhich is cooled by means of a cooling agent,

for example water; however, there may also be used ceramic materal ormetal lined with ceramic material. In the'caseoffa cooled metalcombustion chamber, the heat taken up by the cooling agent can berecovered and used for other purposes.

As starting materifls suitable'for use in the process of this inventionthere can housed the knownihydrocarbons, for example saturated orunsaturated hydrocarbons containing up to 30 or more carbon atoms. Itis. particularly advantageous to employ saturated hydrocarbons, such asmethane, ethane, propane, butane, pentane,- heptane, octane, decanedodecane, especially in the form of liquid commercial mixtures, such aspetroleum distiilates or hydrocarbon oils, for example topped I iuweitoil, aswell as in :the form of technical gases such as earth gas.Instead of aliphatic'saturated hydrocarbons'containing from 1 to about30 or more carbon. atoms, therernay also he used unsaturatedhydrocarbons and hydrocarbons having a branched chain: As branched"hydrocarbons there are concerned, "for example isobutane,isooctane,-isoheptane, isohexane, etc. It is not advisable to useunsaturated hydrocarbons per se unIess it is desired to produceacetylene or unless they are contained inesmall amountsinotherhydrocarbons. Thus, for example; ethylene, propyleneynoriso-butylene-may be used for the production'of acetylene;

As fuels suitable in the production of 'acetylene-and/or ally ortangentially by Way of inlets 5 as; shown in Figure 3. After a shortresidence time in reactor 6, depending on. the dimensions of thereactor, the gases farechilled by means of a cooling agent, for examplefinely divided water introduced by way of lines 7, and separated in asiphon 8 from the liquid ingredients. The reactor, which isadvantageously constructed of metal resistant to high temperature, islined with ceramic material 9. e

We claim: 7 W

1. A process for the manufacture of C -C unsaturated hydrocarbons whichcomprises continuously forming a rotating stream of hot combustiongas ina a combustion zone by introducing an excess of atomized fuel and anoxidizing gas therefor separatelyand tangentially with a velocitycorresponding to a Machnumberof at least 0.8 into the combustion zone,contacting said combustion gas with an atomized aliphatic hydrocarbonfor pyrolysis-thereof, and chilling the effluent mixture of pyrolyzedhydrocarbon and combustion gas.

2. 'A process for the manufacture of C -C unsaturated hydrocarbons whichcomprises continuously-form ing a rotating stream of hot combustiongasina. comb ustion'zone by introducing an excess of atomized fuel and anoxidizing gas therefor separately into thecombustion zone, at least oneof said reactants being'introduced tangentially with a velocitycorresponding to a Mach number of at least 0.8, conducting thecombusti'on gas through a constricted opening or acceleration thereof,contacting said accelerated combustion gas with an atomized aliphatichydrocarbon for pyrolysis thereof, and chilling the effluent mixture ofpyrolyzedhydrocarbon and'combustion gas.

3. A process'for the manufacture of C -C unsaturated hydrocarbons whichcomprises coritinuouslyforming a rotating stream of hot combustion: gasin acombustion zone by introducing an excess 'of atomizedufuel' and anoxidizing gas therefor separately into the .C01I1-' bustion zone, atleastione of said reactants being'intro duced tangentially: with avelocity correspondingitoia Mach number of at least, 0.8, adding asecondary gas selected fromthe group consisting of steam, hydrogen andmixtures thereof to the rotating stream of hot combustion gas,contacting an atomized aliphatic hydrocarbon with the gas mixture thusobtained for pyrolysis of said hydrocarbon, and chilling the effiuentreacted mixture.

4. A process for the manufacture of a product selected from the groupconsisting of acetylene, ethylene and a mixture thereof which comprisescontinuously forming a rotating stream of hot combustion gas byintroducing, separately and at about sonic speed, commercial oxygen andan excess of commercial hydrogen tangentially into a combustion zone;adding a secondary gas selected from the group consisting of steam,hydrogen and mixtures thereof to said rotating stream; thereafterintroducing into the rota-ting stream an aliphatic hydrocarbon ingaseous form for pyrolysis therein; and chilling the reacted mixture.

5. In a process for the manufacture of C -C unsaturated hydrocarbons bycontinuously forming a stream of hot combustion gas in a combustionzone, contacting said combustion gas with an atomized aliphatichydrocarbon for pyrolysis thereof and chilling the efiluent mixture ofpyrolyzed hydrocarbon and combustion gas, the improvement whichcomprises forming a rotating stream of hot combustion gas by introducingan excess of atomized fuel and an oxidizing gas therefor separately intothe combustion zone, at least one of said reactants being introducedtangentially with a velocity corresponding to a Mach number of at least0.8.

6. A process as defined in claim 5 wherein the fuel a and oxidizing gasare introduced at a rate, in relation to the size of the combustionzone, such as to generate at least about a billion kilo calories perhour per cubic meter of combustion chamber.

7. A process as defined in claim 5 wherein at least one of the reactantsis introduced at sonic speed.

8. A process as defined in claim 5 wherein the fuel is hydrogen.

9. A process as defined in claim 5 wherein the oxidizing gas is oxygen.

10. A process as defined in claim 5 wherein the atomized aliphatichydrocarbon is introduced into the combustion gas in a directioncoincident with the direction of rotation of the stream of combustiongas.

11. A process as defined in claim 5 wherein the atomized aliphatichydrocarbon is introduced into the combustion gas in gaseous form.

References Cited in the file of this patent UNITED STATES PATENTS2,343,866 Hincke Mar. 14, 1944 2,599,981 Ekholm June 10, 1952 2,706,210Harris Apr. 12, 1955 2,750,434 Krejci June 12, 1956 2,767,233 Mullen eta1 Oct. 16, 1956 2,813,138 MacQueen Nov. 12, 1957 2,816,941 Goins Dec.17, 1957 2,868,856 Hale et a1. Ian. 13, 1959

4. A PROCESS FOR THE MANUFACTURE OF A PRODUCT SELECTED FROM THE GROUPCONSISTING OF ACETYLENE, ETHYLENE AND A MIXTURE THEREOF WHICH COMPRISESCONTINUOUSLY FORMING A ROTATING STREAM OF HOT COMBUSTION GAS BYINTRODUCING, SEPARATELY AND AT ABOUT SONIC SPEED, COMMERCIAL OXYGEN ANDAN EXCESS OF COMMERCIAL HYDROGEN TANGENTIALLY INTO A COMBUSTION ZONE,ADDING A SECONDARY GAS